The exploding popularity of hand-held digital devices could lead to a big jump in sleep disorders, with experts warning the light emitted from digital screens can have a disturbing effect on the body clock.

Leading Australian researcher Professor Shantha Rajaratnam says there is growing evidence that the night time use of portable digital devices is likely to compound the problems associated with artificial lighting.

"We think that the advent of electric lighting has significantly impacted upon sleep-wake patterns, but with the proliferation of electronic devices that emit light we are expecting that these problems will increase," said Professor Rajatnam, from Monash University's School of Psychology and Psychiatry.

A recent study in the United States showed that devices such as laptops, smart phones and tablets emit approximately 30 to 50 lux, about half the illumination of an ordinary room light.

"We know from preliminary reports that this level of light emission, 30 to 50 lux, is sufficient over a week or so to delay the timing of the circadian clock as well as suppress the production of the hormone melatonin," says Professor Rajaratnam.